Multifrequency Spaceborne Deployable Radiometer Antenna Designs

As part of overall ocean dynamic satellite research, the atmospheric correction microwave radiometer (ACMR) used to correct atmospheric path delay in the radar altimeter has been developed recently. The ACMR, composed of an observing antenna (OA) and calibration antenna, operates at 18.7, 23.8, and 37 GHz for improving atmospheric retrieval accuracy. The dual-polarized OA is realized by an offset deployable dish and the common corrugated horn feeding subsystem, while the calibration antenna uses three corrugated horns. The deployable reflector is made of carbon fiber composite (CFRP) supported by a CFRP frame that connects to the satellite deck, and the deployment of the dish is implemented by two hinges. The feeding subsystem has a loaded-ring corrugated horn, an ultra-wideband orthomode transducer (OMT) that covers almost 2:1 bandwidth ratio and bandpass filters. Compromise is made to guarantee that the root-mean-square errors of the deviation of the phase center from the focal point are as small as possible for the three frequencies. Measured results of the OA showed that the voltage standing-wave ratios (VSWRs) are lower than 1.5 while the cross-polarization levels are below -20 dB throughout the all working bands. Furthermore, the radiation patterns have sidelobe levels below -20 dB, and the antenna main beam efficiencies are all above 90% for the tri-band. The calibration horn antennas have VSWR below 1.2 throughout the tri-band, too. Thermal and vibration tests confirm that the antenna is suitable for space use.